1. Field of the Invention
The present invention relates to a method of subbing photographic supports, more particularly, to a method of subbing plastic film supports for photographic elements employing an aqueous subbing solution containing one or more copolymers of vinylidene chloride and a vinyl monomer having an alcohol group in its side chain to provide tenacious adhesion between a support and aqueous organic colloid layers.
2. Description of the Prior Art
The invention will hereinafter be exemplified using polyester film as an example, which is one representative plastic film.
Polyester film is superior to other supports in properties such as mechanical strength, dimensional stability, heat resistance, chemical resistance, transparency, etc., and has been applied to photographic, printing, drafting, magnetic materials and the like. In recent years, its application has been markedly expanding. In particular, its demand as a photographic film support has rapidly increased in recent years, occupying an important position in photographic film supports.
As is well known, however, it is generally difficult to tenaciously adhere a hydrophilic organic colloid layer such as a photographic emulsion layer to a polyester film support since polyesters are extremely hydrophobic due to their high crystallinity, chemical inertness, lack of a good solvent therefore due to high chemical resistance, and the absence of hydrophilic groups. In the past, there have been many attempts to overcome this problem. One such attempt is to impart good adhesiveness by subbing. For example, the adhesive property of a polyester film can be improved by subbing an unstretched or monoaxially stretched polyester film with an aqueous latex of an acrylate or vinylidene polymer before it is biaxially stretched and thermally treated. This method, however, has a cost disadvantage by reason of, for example, the lack of reusability of a biaxially stretched film prepared by this method.
In order to strengthen the adhesion between a subbing layer and a polyester film, it is also known to heat the film and the subbing layer to a fairly high temperature, or to heat them under pressure. These methods, however, are accompanied by the danger of thermal deterioration of the base.
In order to improve the adhesion between a subbing layer and a hydrophilic organic colloid layer, there has generally been practiced a subbing method using a copolymer of a polymerizable unsaturated carboxylic acid such as acrylic acid, itaconic acid and the like.
As copolymers in which such a polymerizable unsaturated carboxylic acid is used as a copolymerization component, there are, for example, copolymers of an unsaturated carboxylic acid (4 to 12 wt%), styrene or acrylonitrile (30 to 48 wt%) and an acrylate (48 to 70 wt%) as described in U.S. Pat. No. 2,794,742; copolymers consisting of an unsaturated fatty carboxylic acid and at least one ethylenically unsaturated monomer as described in U.S. Pat. No. 3,349,703; copolymers of an unsaturated carboxylic acid and vinylidene chloride as described in published German Patent Application No. 1,811,543; vinyl acetate-acrylate-unsaturated carboxylic acid copolymers as described in Japanese Patent Publication No. 29,995/69; and the like.
These subbing layers, however, have the following disadvantages due to their increased hydrophilicity owing to the acid component, i.e., the carboxylic acids contained therein: Such a subbing layer swells in water, particularly, in an aqueous alkaline solution, resulting in a weakening of its film strength. Consequently, the subbing layer, when applied to a photographic film, is liable to be peeled off in an alkaline developing solution. In addition, the carboxylic acid component in the subbing layer is liable to adversely affect light-sensitive emulsion layers coated thereon, impairing photographic properties such as sensitivity, in particular, under high temperature and high humidity conditions.